Optical medium having a test recording area and method for recording test data thereon

ABSTRACT

A power calibration area is provided for obtaining an optimum recording power and a first information recording area is provided after the power calibration area. A test recording area is formed after the first information recording area for obtaining an optimum recording power for recording information in a next information recording area.

BACKGROUND OF THE INVENTION

The present invention relates to an optical recording medium of a writeonce type and a method for writing and reading information on and fromthe recording medium, and more particularly to the medium which involvespower calibration of a laser beam upon writing.

As a write once type optical recording medium, a CD-R (write once typeCD) is known. In the CD-R, a laser beam is focused on a recordingsurface to convert luminous energy to thermal energy to change thephysical nature of the recording surface. Thus, the information isrecorded on the CD-R.

Although the recording mediums of the same type are made by the samematerial, the individual recording medium has not always the samecharacteristic. Accordingly, if a laser beam is set to a fixed power,information can not be recorded in an optimum condition. Therefore, insuch a recording medium, before recording information, the laser poweris adjusted by an optimum power control (OPC) to be set to an optimumvalue for a disc to be recorded.

A conventional OPC method employed in the CD-R will be described withreference to FIG. 7. The CD-R has a power calibration area (PCA) as atest area, lead-in area LI, information recording area DATA, andlead-out area LO. The PCA is provided on the inside of the lead-in area.A test writing is performed in the test area before recordinginformation so as to obtain an optimum laser power for writinginformation on the CD-R.

More particularly, in order to determine the optimum laser power, in thePCA is recorded a test data, the power of which changes step by stepwithin a predetermined range. When the test data is reproduced, theoptimum recording power can be selected depending on the condition ofthe reproduced data. For example, as shown in FIG. 6a, an EFM pulsesignal having a pulse width such as 3T and 11T is used to stepwiselychange the power of the laser beam emitted from a pickup, therebyrecording the test data. When the test data is reproduced, the frequencylevel and the reproduced waveform are checked to determined the optimumpower.

The test data need not be confined to 3T and 11T data but may be othermodulated data. The modulated data are recorded in the same format asthe ordinary data.

In the write once type CD such as the CD-R, an area in which informationhas been written once is not used for further writing information again.A recorder for writing information is provided for controlling the laserpower by the test writing in the PCA, and for recording information inthe information recording area DATA thereafter with the controlled laserpower.

As shown in FIG. 7, the PCA is divided into about a hundred partitionsor blocks. Since one writing test uses one block, it is possible toperform a hundred times of the OPC.

However, the test writing over a hundred times can not be done.Therefore, even if a writable area (vacant space) remains in theinformation recording area, information can not be recorded therein.

Another drawback of the conventional recording method is caused by thefact that the characteristic of the recording layer is not eventhroughout the entire medium. In the conventional system, the PCA,wherein the test data is recorded, is inside the lead-in area LI so thatthe area is often distant from the information recording area DATA. Thetwo areas may have rather different characteristics. Hence thedetermined laser power appropriate for the PCA may not always beappropriate for the recording area. In order to restrain the drawback,it is necessary to elaborately control the production of the recordinglayer at manufacturing thereof to render the characteristic of the layereven. Thus the manufacturing cost of the optical disc cannot be reduced.

In addition, it would be advantageous if the test data for powercalibration, a procedure of which cannot be omitted at recording, isused to prevent illicit copying of data.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an inexpensive writeonce optical recording medium and recording method thereof, wherein thenumber of recordings is increased.

Another object is to provide a method for recording data on the opticalmedium and reproducing the recorded data wherein illicit copying of datais prevented.

According to the present invention, there is provided an opticalrecording medium having a power calibration area for obtaining anoptimum recording power and a first information recording area after thepower calibration area, comprising, a test recording area, in which atest data is recorded, being provided after the first informationrecording area for obtaining an optimum recording power for recordinginformation in a next information recording area. The test recordingarea is provided as an indication area for partitioning betweeninformation recorded areas.

The present invention further provides a method for recordinginformation on an optical recording medium, comprising the steps of,providing a test recording area after a first information recordingarea, recording a test data in the test recording area, obtaining anoptimum recording power by reproducing the test data recorded on thetest recording area, recording information on a next information areaafter the test recording area with a light beam at the obtained optimumrecording power.

The method further comprises setting the test recording area to anindication area for partitioning between information recording areas.

In an aspect of the present invention, the test data has a predeterminedpattern.

The method further comprises comparing the reproduced test data with thepredetermined pattern, disabling the step of recording information onthe next information recording area when the reproduced test data doesnot coincide with the predetermined pattern.

These and other objects and features of the present invention willbecome more apparent from the following detailed description withreference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1a is a diagram showing a format for recording data on the writabledisc in accordance with the present invention;

FIG. 1b is a diagram showing a data format of the data recorded on thedisc;

FIG. 2 is a block diagram of a system for recording and reading data onand from a writable optical disc according to the present invention;

FIG. 3 is a flowchart describing the operation of the system of FIG. 2when recording data;

FIG. 4 is a flowchart describing a modified operation for recordingdata;

FIG. 5 is a flowchart describing the operation when reading out datarecorded in accordance with the operation of FIG. 4;

FIGS. 6a and 6b are charts each showing changing pattern of laser powerof a test data; and

FIG. 7 is a diagram showing a conventional format for recording data onthe writable disc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The principle of the present invention is described with reference toFIGS. 1a and 1b, showing the recording format according to the presentinvention, and a data format, respectively.

Referring to FIG. 1a, in an optical medium, hereinafter referred to asan optical disc, the power calibration area PCA, lead-in area LI and thelead-out area LO are formed as in the conventional format shown in FIG.7. The power calibration area PCA of the present invention need not bedivided into one hundred blocks. It suffices if only one block isprovided to enable the calibration once. The lead-in area LI andlead-out area LO are provided before an information recording area DATAof a first recording area, which is herein referred to as a chapter, andafter an information recording area of a last chapter where the lastrecording data for the disc are stored, respectively.

Each chapter is provided with a management information area MA in frontof the area DATA for recording a management information, and a partitiondata area PA at the rear of the area DATA for indicating the lastrecording position.

The data recorded in each area is formatted as shown in FIG. 1b. Namely,a synchronizing signal SYNC and a sector number S# are written at everypredetermined length of each data.

More particularly, at a first recording when a Chapter 1 is recorded,the test data for power calibration is recorded in the power calibrationarea PCA. The management information and the recording data are written,thereby forming the management area MA and the recording area DATA.Thereafter, the partition area PA of the Chapter 1 is formed by writingonly the synchronizing signal SYNC and the sector number S#.

When recording Chapter 2, the management area MA of the Chapter 1 isread to obtain the address of the partition area PA in the Chapter 1.The partition area PA of the Chapter 1 is read to determine whether thetest data is recorded therein. If the partition area PA is a blank, thetest data for writing data in the Chapter 2 is recorded in the blankpartition area PA of the Chapter 1 for determining the optimum laserpower. Thereafter, the management information and the data are writtenin the areas MA and DATA of the Chapter 2, and the partition area PA iskept unwritten except for the synchronizing signal SYNC and the sectornumber S#. Hence, although the recording is repeated a number of times,the partition area of the last chapter is kept blank, so that the lastrecording position can be easily detected. When the recording iscompleted, a lead-out data is written in the lead-out area LO.

A system for thus recording information on an optical disc and forreading the information is described hereinafter with reference to FIG.2.

A recording data signal to be recorded on a writable optical disc (CD-R)1 is applied to an encoder 6 through a CPU 11 in accordance with theoperation of a user. The encoded signal is fed to a laser 5 so that theoutput thereof is modulated. A laser beam corresponding to the datasignal is emitted from the laser 5 and transmitted through a pickup 3 soas to be focused on the optical disc 1 which is driven by a motor 2.

A laser power control circuit 7 is provided to control the power of thelaser beam at the optimum level. Namely, a test data is recorded in thePCA or the partition areas PA. The reproduced test data is applied to areproducing signal amplifier 8 through the pickup 3. The reproduced testdata is decoded at a guide signal decoder 10 and fed to the CPU 11. TheCPU 11 determines the optimum power applied at recording, andaccordingly applies a power control signal to the laser power controller7, thereby to control the power.

A reproduced data signal is read by the pickup 3 and applied to thereproducing signal amplifier 8. The reproduced signal is decoded at adecoder 9 and outputted through the CPU 11.

The reproduced signal from the amplifier 8 is applied to a servo circuit4 through the guide signal decoder 10. The decoded reproduced datasignal is also fed to the servo circuit 4. The servo circuit 4 controlsthe pickup 3 and the motor 2 in accordance with the reproduced signals,thereby operating a focus servo system, track-following servo system andthe spindle servo system.

The operation of the system when recording data on the disc 1 isdescribed hereinafter with reference to the flowchart of FIG. 3.

At a step S1, it is confirmed that the disc 1 is set at the correctmounting position. Namely, the system is arranged such that if the discis correctly set, the focusing operation can be performed. The positionis confirmed by moving the pickup 3 to a predetermined radial positionof the disc 1. Thereafter at a step S2, the motor 2 is operated to drivethe disc 1, and at the same time, servo systems such as the focus servosystem and the track-following system are checked to confirm whetherthey are normally operated for accurately recording and readinginformation.

At a step S3, the pickup 3 is moved to the power calibration area PCA ofthe disc 1 in accordance with the address information which is outputtedfrom the guide signal decoder 10. At a step S4, the power calibrationarea PCA is checked. Namely, the strength of the laser beam emitted fromthe pickup 3 to the disc 1 is set to a small value for reproducing data.The reproducing signal amplifier 8 and the decoder 9 are operated so asto read out data in the power calibration area PCA while the servocircuit 4 is operated. Since the power calibration is necessarilyexecuted before each recording, if data is already written in theChapter 1, the test data is recorded in the power calibration area PCA.Thus, at a step S5, by reading the power calibration area PCA, it can bedetermined whether the disc 1 is a blank disc where data has never beenrecorded, or a disc is written at least on the Chapter 1.

When it is determined that the disc is a blank disc at the step S5, theprogram goes to a step S6 to carry out power calibration, the operationof which is already described hereinbefore with connection to theconventional recording method. Thereafter, at a step S7, the strength ofthe laser beam is set to the optimum power determined at the step S6,and the lead-in data is written, thereby to form the lead-in area LI.

At step S14, the management area MA of the Chapter 1 is formed withoutwriting information at this time. Thereafter, the recording data iswritten in the data recording area DATA of the Chapter 1 at step S15. Atstep S16, the partition area PA of the Chapter 1 is formed by writingthe synchronizing signal SYNC and the sector number S#. Finally, themanagement information such as the directory of the data and the addressof the corresponding partition area, that is the partition area PA ofthe Chapter 1, is recorded in the management area MA of the Chapter 1 atstep S17.

If it is determined at the step S5 that data is already written on apart of the disc 1, the program goes to a step S8 where the managementinformation of the Chapter 1 is read out. At a step S9, the pickup 3 ismoved to the address of the partition area PA. The address is includedin the management information obtained at the step S8. At a step S10,the partition area PA is read out.

At a step S11, when there is no test data recorded in the partition areaPA, it means that the Chapter 1 is the last recorded area. Thereafter,the program proceeds to a step S13 where the test data for recordingdata in the Chapter 2 is recorded in the partition area PA of theChapter 1.

When the test data is read out at the step S10, it means that otherchapters are written subsequent to the Chapter 1. The programaccordingly goes from the step S11 to a step S12 where the pickup 3 ismoved to a management area MA of the next chapter, namely, Chapter 2.The management information of the Chapter 2 is read out from themanagement area MA to obtain the partition address of the Chapter 2.Thereafter, the steps S9 and S10 are carried out to read the partitionarea PA of the Chapter 2. The steps S9 through S12 are repeated untilthe last written chapter is determined. After the last chapter is foundat the step S11, the power calibration is performed at the step 13 usingthe blank partition area PA of the last recorded chapter.

Thereafter, the program goes to the steps S14 and S15 so that themanagement area MA is formed and the recording data is written in therecording area DATA, respectively. Furthermore, at steps S16 and S17,the partition area PA of the newly written chapter is formed and theaddress of the newly formed partition area PA is written in themanagement area MA.

Hence, in accordance with the present invention, the power calibrationis carried out in a part of the disc adjacent the area where therecording data is to be actually written.

FIG. 4 shows a flowchart of the operation according to a modification ofthe present invention, wherein illicit copying of data can be prevented.The operation of FIG. 4 is similar to that shown in FIG. 3 so that thedescriptions of the identical steps designated by the same numbers areomitted.

In accordance with the present modification, the test data recorded atthe steps S6 and S13 for determining the optimum laser power has apredetermined special pattern as shown in FIG. 6b, for example. Namely,the power of the test data signal need not change stepwisely as shown inFIG. 6a, but can be set to any pattern without affecting the powercalibration as long as a predetermined resolution is satisfied. Thelegitimacy of the recordings can be detected by comparing the powerpattern of the recorded test data with the predetermined pattern.

More particularly, when it is detected at the step S5 that data isalready recorded on the set disc, the program goes to a step S20 wherethe pattern of the test data read out from the power calibration areaPCA at the step S4 is compared with the predetermined pattern. If thepatterns coincide with each other, it means that the Chapter 1 islawfully written on the disc using a legitimate recording device. Hencethe program goes to the step S8 to execute further procedure forrecording.

When the power pattern of the read out test data differs from thepredetermined pattern, it means that the Chapter 1 was illicitlyrecorded. Hence the program is ended, thereby preventing furtherrecording.

The test data recorded at other recordings are further checked. Namely,if there are other chapters recorded besides the Chapter 1, the programgoes from the step S11 to a step S21 where the test data recorded in thepartition area PA of the next chapter is checked. When the pattern ofthe test data coincides with the predetermined pattern, the programproceeds to the step S12. When the patterns do not coincide, the programis ended. Thus, the data cannot be recorded unless all of the chaptersare recorded on a legitimate device, thereby preventing illicit copyingof data.

The power pattern of the test data is determined by agreement betweenthe copyright holder of the data and the manufacturer-of the recordingand reproducing devices.

FIG. 5 is a flowchart showing operation wherein illicitly recorded datacannot be reproduced.

Referring to FIG. 5, at a step S31, it is confirmed that the disc 1 isset at the correct position and at a step S32, the servo systems arealso checked. Thereafter, at a step S33, the management information isread out from the management area of the Chapter 1, and at a step S34,the partition area PA thereof is searched dependent on the partitionaddress included in the management information. Thereafter at a stepS35, the test data is read out from the partition area PA.

When it is determined at a step S36 that the pattern of the read outtest data coincides with the predetermined pattern, the program proceedsto a step S37 where the data recorded on the disc is reproduced. Whenthe pattern of the read out test data does not coincide with thepredetermined pattern, the program is ended at once.

The power pattern of the test data may be detected during the operationsshown in FIGS. 4 and 5 in accordance with the change of the level of thereproduced RF signal. Alternatively, the change of integrated values ofthe reproduced signal may be detected. Furthermore, errors in thereproduced signal is counted to detect the change in the frequency ofthe errors.

In the case of an exclusive reproducing device for only reproducingdata, the pickup is not capable of moving to the power calibration area,which is formed inside the lead-in area, so that the data in the powercalibration area-cannot be read out. However, in accordance with thepresent modification, the test data is recorded in the partition areasPA which is within the data recording area. Thus the test data can bereproduced.

The test data can be used for identifying other qualities of the databesides the legitimacy thereof.

The present invention can be applied to other type of optical recordingmedium such as a phase change disc.

From the foregoing it will be understood that in accordance with thepresent invention, the test data for determining optimum power isrecorded in an area adjacent the actual recording area. Since thecharacteristics of the recording layers of both areas are similar, theoptimum power for the recording area can be determined. Hence theforming of the recording layer need not be strictly controlled, therebyreducing the overall manufacturing cost of the optical disc. Moreover,the test data is recorded in the partition area for indicating the lastrecorded position and not in the power calibration area, the area ofwhich is limited. Hence the data can be recorded as many times as neededwithout regard to the number of blocks in the power calibration area sothat the entire recording area can be effectively used.

Moreover, in accordance with the present invention, the power of thelegitimate test data for determining the optimum laser power is adaptedto change depending on a predetermined pattern. When the reproduced testdata does not coincide with the power pattern, showing that illicitrecording was carried out on the disc, the recording operation or thereproducing operation is immediately stopped. Thus the illicit copyingof data can be prevented.

What is claimed is:
 1. An optical recording medium having a powercalibration area for obtaining an optimum recording power and a firstinformation recording area after the power calibration area,comprising:a partition area provided after the first informationrecording area for partitioning the first information recording area anda next second information recording area, being provided as anotherpower calibration area in which a test data is recorded for obtaining anoptimum recording power for recording information in the next secondinformation recording area when no test data is recorded in thepartition area.
 2. An optical recording medium according to claim 1,further comprising a management information recording area in which anaddress of the partition area is recorded.
 3. An optical recordingmedium according to claim 2, wherein the management informationrecording area is formed in front of the first information recordingarea.